package com.way.pulltorefresh;

import android.annotation.TargetApi;
import android.os.Build;
import android.util.Log;
import android.view.View;

import com.way.pulltorefresh.PullToRefreshBase.Mode;
import com.way.pulltorefresh.PullToRefreshBase.State;

@TargetApi(Build.VERSION_CODES.GINGERBREAD)
public final class OverscrollHelper {

	static final String LOG_TAG = "OverscrollHelper";
	static final float DEFAULT_OVERSCROLL_SCALE = 1f;

	/**
	 * Helper method for Overscrolling that encapsulates all of the necessary
	 * function.
	 * <p/>
	 * This should only be used on AdapterView's such as ListView as it just
	 * calls through to overScrollBy() with the scrollRange = 0. AdapterView's
	 * do not have a scroll range (i.e. getScrollY() doesn't work).
	 * 
	 * @param view
	 *            - PullToRefreshView that is calling this.
	 * @param deltaX
	 *            - Change in X in pixels, passed through from from overScrollBy
	 *            call
	 * @param scrollX
	 *            - Current X scroll value in pixels before applying deltaY,
	 *            passed through from from overScrollBy call
	 * @param deltaY
	 *            - Change in Y in pixels, passed through from from overScrollBy
	 *            call
	 * @param scrollY
	 *            - Current Y scroll value in pixels before applying deltaY,
	 *            passed through from from overScrollBy call
	 * @param isTouchEvent
	 *            - true if this scroll operation is the result of a touch
	 *            event, passed through from from overScrollBy call
	 */
	public static void overScrollBy(final PullToRefreshBase<?> view,
			final int deltaX, final int scrollX, final int deltaY,
			final int scrollY, final boolean isTouchEvent) {
		overScrollBy(view, deltaX, scrollX, deltaY, scrollY, 0, isTouchEvent);
	}

	/**
	 * Helper method for Overscrolling that encapsulates all of the necessary
	 * function. This version of the call is used for Views that need to specify
	 * a Scroll Range but scroll back to it's edge correctly.
	 * 
	 * @param view
	 *            - PullToRefreshView that is calling this.
	 * @param deltaX
	 *            - Change in X in pixels, passed through from from overScrollBy
	 *            call
	 * @param scrollX
	 *            - Current X scroll value in pixels before applying deltaY,
	 *            passed through from from overScrollBy call
	 * @param deltaY
	 *            - Change in Y in pixels, passed through from from overScrollBy
	 *            call
	 * @param scrollY
	 *            - Current Y scroll value in pixels before applying deltaY,
	 *            passed through from from overScrollBy call
	 * @param scrollRange
	 *            - Scroll Range of the View, specifically needed for ScrollView
	 * @param isTouchEvent
	 *            - true if this scroll operation is the result of a touch
	 *            event, passed through from from overScrollBy call
	 */
	public static void overScrollBy(final PullToRefreshBase<?> view,
			final int deltaX, final int scrollX, final int deltaY,
			final int scrollY, final int scrollRange, final boolean isTouchEvent) {
		overScrollBy(view, deltaX, scrollX, deltaY, scrollY, scrollRange, 0,
				DEFAULT_OVERSCROLL_SCALE, isTouchEvent);
	}

	/**
	 * Helper method for Overscrolling that encapsulates all of the necessary
	 * function. This is the advanced version of the call.
	 * 
	 * @param view
	 *            - PullToRefreshView that is calling this.
	 * @param deltaX
	 *            - Change in X in pixels, passed through from from overScrollBy
	 *            call
	 * @param scrollX
	 *            - Current X scroll value in pixels before applying deltaY,
	 *            passed through from from overScrollBy call
	 * @param deltaY
	 *            - Change in Y in pixels, passed through from from overScrollBy
	 *            call
	 * @param scrollY
	 *            - Current Y scroll value in pixels before applying deltaY,
	 *            passed through from from overScrollBy call
	 * @param scrollRange
	 *            - Scroll Range of the View, specifically needed for ScrollView
	 * @param fuzzyThreshold
	 *            - Threshold for which the values how fuzzy we should treat the
	 *            other values. Needed for WebView as it doesn't always scroll
	 *            back to it's edge. 0 = no fuzziness.
	 * @param scaleFactor
	 *            - Scale Factor for overscroll amount
	 * @param isTouchEvent
	 *            - true if this scroll operation is the result of a touch
	 *            event, passed through from from overScrollBy call
	 */
	public static void overScrollBy(final PullToRefreshBase<?> view,
			final int deltaX, final int scrollX, final int deltaY,
			final int scrollY, final int scrollRange, final int fuzzyThreshold,
			final float scaleFactor, final boolean isTouchEvent) {

		final int deltaValue, currentScrollValue, scrollValue;
		switch (view.getPullToRefreshScrollDirection()) {
		case HORIZONTAL:
			deltaValue = deltaX;
			scrollValue = scrollX;
			currentScrollValue = view.getScrollX();
			break;
		case VERTICAL:
		default:
			deltaValue = deltaY;
			scrollValue = scrollY;
			currentScrollValue = view.getScrollY();
			break;
		}

		// Check that OverScroll is enabled and that we're not currently
		// refreshing.
		if (view.isPullToRefreshOverScrollEnabled() && !view.isRefreshing()) {
			final Mode mode = view.getMode();

			// Check that Pull-to-Refresh is enabled, and the event isn't from
			// touch
			if (mode.permitsPullToRefresh() && !isTouchEvent && deltaValue != 0) {
				final int newScrollValue = (deltaValue + scrollValue);

				if (PullToRefreshBase.DEBUG) {
					Log.d(LOG_TAG, "OverScroll. DeltaX: " + deltaX
							+ ", ScrollX: " + scrollX + ", DeltaY: " + deltaY
							+ ", ScrollY: " + scrollY + ", NewY: "
							+ newScrollValue + ", ScrollRange: " + scrollRange
							+ ", CurrentScroll: " + currentScrollValue);
				}

				if (newScrollValue < (0 - fuzzyThreshold)) {
					// Check the mode supports the overscroll direction, and
					// then move scroll
					if (mode.showHeaderLoadingLayout()) {
						// If we're currently at zero, we're about to start
						// overscrolling, so change the state
						if (currentScrollValue == 0) {
							view.setState(State.OVERSCROLLING);
						}

						view.setHeaderScroll((int) (scaleFactor * (currentScrollValue + newScrollValue)));
					}
				} else if (newScrollValue > (scrollRange + fuzzyThreshold)) {
					// Check the mode supports the overscroll direction, and
					// then move scroll
					if (mode.showFooterLoadingLayout()) {
						// If we're currently at zero, we're about to start
						// overscrolling, so change the state
						if (currentScrollValue == 0) {
							view.setState(State.OVERSCROLLING);
						}

						view.setHeaderScroll((int) (scaleFactor * (currentScrollValue
								+ newScrollValue - scrollRange)));
					}
				} else if (Math.abs(newScrollValue) <= fuzzyThreshold
						|| Math.abs(newScrollValue - scrollRange) <= fuzzyThreshold) {
					// Means we've stopped overscrolling, so scroll back to 0
					view.setState(State.RESET);
				}
			} else if (isTouchEvent && State.OVERSCROLLING == view.getState()) {
				// This condition means that we were overscrolling from a fling,
				// but the user has touched the View and is now overscrolling
				// from touch instead. We need to just reset.
				view.setState(State.RESET);
			}
		}
	}

	static boolean isAndroidOverScrollEnabled(View view) {
		return view.getOverScrollMode() != View.OVER_SCROLL_NEVER;
	}
}
